My hand draws back. I often sigh still (9)
Here's the "now" part. The transformation is the passage of time, or aging of the speaker. This change is pretty universal. We're all getting older by the minute.
as they cropped up tons of mush and grassto gouge their underworld garage (15–16).
Here's an example of physical transformation. They're digging up the place. Nothing says change like good old fashioned destruction!
Parking spaces luxuriate like civicsandpiles in the heart of Boston (17–18)
More physical change, and a seemingly negative one. Parking spaces are what are at the heart of Boston, and parking spaces don't exactly scream character. Bummer.